Transistorized ignition system



United States Patent 3,434,463 TRANSISTORIZED IGNITION SYSTEM HerbertBartch, 2311 SE. 148th Ave., Portland, Oreg. 97233 Filed Jan. 30, 1967,Ser. No. 612,502

Int. Cl. F02p 3/04 US. Cl. 123-148 12 Claims ABSTRACT OF THE DISCLOSURESUMMARY OF THE INVENTION This invention relates to ignition systems forinternal combustion engines, and more particularly to an ignition systemwhich functions to provide optimum performance and maximum efiiciencyover a wide range of engine speeds.

This invention is an improvement over the system invented by William V.Guyton and myself and disclosed in US. Letters Patent No. 3,288,125.

Prior to the invention disclosed in the aforementioned patent,conventional ignition systems utilized a current limiting resistance,commonly called a ballast resistor, between the potential source and theprimary winding of the ignition transformer. However, sufficientvariations in current still are developed in such systems during engineoperation as to adversely affect the performance of the latter and theservice life of the system components.

Further, in such prior systems, as well as in the systerns disclosed inthe aforementioned patent, the use of a points condenser in parallelwith the ignition breaker points allows the alternating current tocirculate through the entire ignition system, thereby reducingeificiency and creating deleterious interference signals.

Still further, use of a breaker points condenser in such ignitionsystems requires that its reactance be matched to the entire electricalsystem in order to obtain the highest Q factor for maximum efiiciency ofoperation, and this is difficult to achieve.

The present invention achieves the principal objective of overcoming theforegoing disadvantages while simultaneously eliminating from theignition system the conventionally employed breaker points condenserand, preferably, the ballast resistor also. The ignition system of thepresent invention thus is of more simplified construction for moreeconomical manufacture, and provides long and faithful service with aminimum of maintenance and repair.

The foregoing and other objectives and advantages of the presentinvention will appear from the following detailed description, taken inconnection with the accompanying drawings of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 are schematicelectrical diagrams of 'various forms of the ignition system embodyingthe features of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventional internalcombustion engines have ignition systems in which a source of electricpotential, such as the battery 10, is releasably connected sequentiallythrough an ignition key start switch 12 and running switch 14 to theprimary winding 16 of an ignition transformer 18. The steppedup voltageat the secondary winding 20, which is controlled by the cam-operatedbreaker points 22, is fed through the common rotor contact 24 of thedistributor (not shown) sequentially to the several spark plugs of theengine.

As explained hereinbefore, conventional ignition systems heretofore haveutilized a breaker points condenser connected in parallel with thebreaker points 22. It is an important feature of the present inventionthat such a condenser is eliminated, together with its disadvantagesenumerated hereinbefore.

In accordance with the present invention, a capacitor 26 is connectedacross the primary winding 16 to form with the latter an L-C tankcircuit which provides a closed alternating current circulating pathindependent of the source 10 of electric potential.

A bypass capacitor 28 is connected across the series circuit arrangementof the points 22 and L-C tank circuit, to insure that substantially allof the alternating current voltage across the points will appear acrossthe tank circuit.

Moreover, the high circulating current thus provided is isolated fromthe battery circuit by the breaker points 22 which are open during thattime. Accordingly, the highest Q factor and consequently the maximumefficiency of system operation, is achieved merely by matching thereactances of the capacitor 26 and the primary winding 16.

Means also preferably is provided in the ignition system of the presentinvention to achieve maximum stabilization of primary winding current.

Referring first to FIG. 1 of the drawings, wherein a negative groundignition system is illustrated, there is interposed between the ignitionkey running switch 14- and the positive end of the primary winding 16 ofthe ignition transformer the series arrangement of the emitter currentlimiting resistance 30 and the emittercollector of the transistor 32.The base of the transistor is connected through the biasing resistance34 to the negative side of the battery .10, herein shown as ground.

Shunting the series arrangement of the emitter current limitingresistance 30 and the emitter-base junction of the transistor 32 is thediode rectifier 36. This diode provides a regulated source of biasvoltage at the transistor base, the magnitude of which is defined overnarrow limits by the value of the biasing resistance 34. Thus, assumingthere is a substantially constant voltage in shunt with the seriesarrangement of resistance 30 and the emitter-base junction, any changein current through the emitter will cause a corresponding change involtage drop across the resistance 30. This, in turn, produces acorresponding but inverse change in available voltage across theemitter-base junction and a corresponding compensating change in currentthrough the emittercollector circuit, thereby maintaining said currentsubstantially constant.

Accordingly, the diode functions to provide a substantially constantvoltage which, in conjunction with resistance 30 and the emitter-basejunction, provides a substantially constant current through thetransistor collector, breaker points 22, ignition transformer 18 andspark plugs, regardless of changes in battery voltage, faulty regulator,or faulty transformer. Moreover, this substantially constant current isprovided over the operating range of the engine, thus providing lowerpoints current at low speeds and higher output voltage at higher speedsas compared with conventional systems. The lower points current at lowerspeeds effctively decreases ignition noise,

with consequent reduction in radio interference, and extends the life ofthe breaker points, spark plugs and all other ignition components. Thehigher output voltage at higher engine speeds affords ellicientoperation of the engine at speeds higher than those attainable withconventional ignition systems.

The use of the diode also provides automatic temperature compensationfor the system. For example, as the components of the system increase intemperature the required voltage across the transistor base-emittercircuit for a given current drops, and simultaneously the voltage acrossthe diode also drops.

The circuit illustrated in FIG. 2 as adapted for positive groundignition systems. In this instance the breaker points 22 are connectedto the common positive ground, the junction of the resistance 30 and thediode 36 is connected to the end of the primary winding 16 opposite thebreaker points, and the junction of the collector and base biasresistance 34 is connected through the running switch 14 to the negativeterminal of the battery In the embodiment illustrated in FIG. 3, thetransistor is interposed between the breaker points 22 and the negativeground terminal of the battery.

The embodiment of FIG. 3 also includes a relay 38 the normally openswitch contact 40 of which is connected across the emitter-collector ofthe transistor 32. The relay coil is connected across the battery .10through the start switch 12 of the ignition key switch. Accordingly, forthe short period of time during starting of the engine that the startswitch 12 is closed, the relay switch contact 40 also closes, thusbypassing the transistor circuit to provide higher initial startingvoltage, in conventional manner.

Since the high circulating current in the tank circuit is isolated fromthe circuit of the battery -10, switch 14 and transistor 32, by virtueof the open breaker points 22 which, in the present invention, are notshunted by a points condenser, the transistor does not requireprotection by a shunting capacitor. Such a shunting capacitor has theadverse effect of creating a low frequency curent oscillation while thebreaker points are closed, causing the output voltage of the transformersecondary to drop periodically to levels which may cause engine misfireat certain speeds. This occurs because the length of time the points areclosed changes with engine speed, and charging current variations withrespect to time show up in the secondary winding as voltage variations,since the charging rate of the coil remains constant.

In the operation of the ignition system of the present invention, theignition key is manipulated first to close both the starting switch 12and the running switch 14. Closure of the starting switch by-passes thetransistor circuitry, either directly in the embodiments of FIGS. 1 and2, or through operation of the relay 38 in the em,- bodiment of FIG. 3,to provide higher ignition starting voltage, as previously explained.Upon starting of the engine the ignition key is moved to the position atwhich the starting switch 12 opens and the running switch 14 remainsclosed. The substantially constant current provided by the transistorcircuitry is maintained regardless of variations in the ignitioncomponents, battery voltage and engine speed. Thus, more uniformignition is achieved at all speeds throughout the extended range of theengine operation, and the service life of the breaker points, sparkplugs and other ignition components is substantially increased. Thesefactors reduce materially the incidence of necessary tune-ups andcomponent replacements and also contributes to improve economy ofoperation.

Moreover, the provision in the present invention of the series circuitarrangement of the resonant L-C tank circuit 16, 26 and the breakerpoints 22 shunted by the bypass capacitor 28, provides maximumefliciency of operation by the development of high circulating currentwhich is isolated from the battery circuit. This is achieved whether thesystem includes the transistorized current regulator described, or aconventional ballast resistor, or no regulation at all.

Typical values of components for the circuits described hereinbefore areas follows: Resistance 30 about 0.15 ohms; resistance 34 about to 150ohms, preferably about ohms; capacitor 26 about 0.18 microfarad; andcapacitor 28 about 0.5 microfarad. A suitable diode is Motorola 1N400=l,and a suitable transistor is Motorola 2N1544.

The ignition system of the present invention may be provided as acomplete and integral system, as illustrated in the drawings, or it maybe provided in kit form for modifying existing conventional systems byremoving from the latter the ballast resistor and the breaker pointscondenser. In FIGS. 1 and 2 the kit comprises the components 2636, whilein FIG. 3 the kit comprises the components 26-40.

It will be apparent to those skilled in the art that various changes maybe made in the number, type, value and arrangement of componentsdescribed hereinbefore. For example, although the transistorized currentregulator is preferred for its improved performance, a conventionalballast resistor may be employed. About 20% increase in output powerover conventional systems is obtained by virtue of the association withsuch ballast resistor of the LC tank circuit and bypass capacitorarrangement described hereinbefore. In this case bypass capacitor 28 ischosen to be about 2000 microfarads. These and other changes may be madewithout departing from the spirit of this invention and the scope of theappended claims.

Having now described my invention and the manner in which it may beused, I claim:

1. A kit for use in increasing the efiiciency of an ignition system foran engine having the series circuit arrangement of an ignitiontransformer primary winding and breaker points normally connected acrossa source of electric potential, the system being characterized by theabsence of an ignition condenser across said points, the kit comprising(a) a capacitor,

(b) means for connecting the capacitor across the primary winding forforming with the latter an L-C tank circuit for providing a closedalternating current circulating path independent of the source ofelectric potential,

(c) bypass capacitance means, and

(d) means for connecting the bypass capacitance means in parallel withthe series circuit arrangement of said L-C circuit and breaker points.

2. The kit of claim 1 including a current regulator comprising (a) atransistor,

(b) means for connecting the collector and emitter of the transistor inseries with the breaker points and primary Winding,

(c) base bias voltage resistance means connected to the transistor base,

(d) means for connecting the base bias voltage resistance means to thesource of electric potential,

(e) emitter current limiting resistance means connected to thetransistor emitter,

(f) means for connecting the emitter current limiting resistance meansto the source of electric potential, and

(g) bias voltage source means connected across the series arrangement ofthe emitter current limiting resistance means and the emitter-basejunction of the transistor for providing substantially constant biasvoltage across said series arrangement and substantially constantcurrent through the emitter-collector circuit.

3. The kit of claim 2 wherein the collector and emitter are adapted tobe connected between the primary winding and the positive terminal ofthe source of electric potential.

4. The kit of claim 2 wherein the collector and emitter are adapted tobe connected between the primary winding and the negative terminal ofthe source of electric potential.

5. The kit of claim 2 wherein the collector and emittter are adapted tobe connected between the breaker points and one terminal of the sourceof electric potential.

6. The kit of claim 5 wherein the system includes an ignition switchhaving a start switch and a running switch, and wherein the kit includes(a) starter switch means connected across the transistoremitter-collector for releasably shunting the latter,

(b) electrical actuator means for the starter switch means and having anelectric circuit, and

(c) means for connecting the start switch of the ignition switch inseries in said actuator circuit.

7. An ignition system for an engine, comprising (a) a source of electricpotential,

(b) an ignition transformer including primary and secondary windings,

(c) breaker points connected in series with the primary winding andreleasably connecting said series circuit across the source of electricpotential,

(d) a capacitor connected across the primary winding and forming withthe latter an LC tank circuit for providing a closed alternating currentcirculating path independent of the source of electric potential, and

(e) bypass capacitance means connected in parallel with the seriescircuit arrangement of said LC circuit and breaker points,

(f) the ignition system being characterized by the absence of a breakerpoints ignition condenser in parallel with said points.

8. The system of claim 7 including a current regulator comprising (a) atransistor,

(b) the collector and emitter of the transistor being connected inseries with the breaker points and primary winding,

(c) base bias voltage resistance means connecting the transistor base tothe source of electric potential,

(d) emitter current limiting resistance means connecting the transistoremitter to the source of electric potential, and

(e) bias voltage source means connected across the series arrangement ofthe emitter current limiting resistance means and the emitter-basejunction of the transistor for providing substantially constant biasvoltage across said series arrangement and substantially constantcurrent through the emitter-collector circuit.

9. The system of claim 8 wherein the transistor collector and emitterare connected between the primary winding and the positive terminal ofthe source of electric potential.

10. The system of claim 8 wherein the transistor collector and emitterare connected between the primary winding and the negative terminal ofthe source of electric potential.

11. The system of claim 8 wherein the transistor collector and emitterare connected between the breaker points and one terminal of the sourceof electric potential.

12. The system of claim 11 including (a) starter switch means connectedacross the transistor emitter-collector for releasably shunting thelatter,

(b) electrical actuator means for the starter switch means and having anelectric circuit connected to the source of electric potential, and

(c) a start switch in the circuit of the actuator means and operablemomentarily during starting of the engine to effect shunting of thetransistor emittercollector.

References Cited UNITED STATES PATENTS 2,898,392 8/1959 Jaeschke.3,288,125 11/1966 Guyton et a1. 3,324,351 6/ 1967 Pahl 315219 LAURENCEM. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 315209

